function to match parenthesis '(' and ')'

[Steve Kirsch]

I need a simple function that can match the number of beginning and ending
parenthesis in an expression. Here's a sample expression:

( ( "john" ) and ( "jane" ) and ( "joe" ) )

Does .NET have something built-in that can accomplish this, or do I have to
write my own parser? I don't want to reinvent the wheel if possible.

[Paul E Collins]

"Steve Kirsch" <te**@test.co m> wrote:

I need a simple function that can match the number
of beginning and ending parenthesis in an expression.
Here's a sample expression:
( ( "john" ) and ( "jane" ) and ( "joe" ) )

There's nothing in the Framework to count the number of occurrences of
a character in a string, but you can find any one occurrence with
String.IndexOf, and do this in a loop to count them all. (Each time
you find one, increment the start position and loop back.)

P.

[ALI RAZA]

Salam

The simple solution to this problem is to implement a stack, when u
encounter '(' push it on the stack, and when u encounter ')', pop it from
the stack.

In the End, check if the stach is empty, if it is empty then the parenthesis
are match else they are not.

--
ALI RAZA SHAIKH
MCAD.net

www.programmersparadise.cjb.net
alirazashaikh.b logspot.com
"Steve Kirsch" <te**@test.co m> wrote in message
news:%2******** ********@TK2MSF TNGP15.phx.gbl. ..

I need a simple function that can match the number of beginning and ending
parenthesis in an expression. Here's a sample expression:

( ( "john" ) and ( "jane" ) and ( "joe" ) )

Does .NET have something built-in that can accomplish this, or do I have
to write my own parser? I don't want to reinvent the wheel if possible.

[ALI RAZA]

Salam

The simple solution to this problem is to implement a stack, when u
encounter '(' push it on the stack, and when u encounter ')', pop it from
the stack.

In the End, check if the stach is empty, if it is empty then the parenthesis
are match else they are not.
--
ALI RAZA SHAIKH
MCAD.net

www.programmersparadise.cjb.net
alirazashaikh.b logspot.com

"Steve Kirsch" <te**@test.co m> wrote in message
news:%2******** ********@TK2MSF TNGP15.phx.gbl. ..

I need a simple function that can match the number of beginning and ending
parenthesis in an expression. Here's a sample expression:

( ( "john" ) and ( "jane" ) and ( "joe" ) )

Does .NET have something built-in that can accomplish this, or do I have
to write my own parser? I don't want to reinvent the wheel if possible.

[Marcus Andrén]

On Sat, 22 Oct 2005 15:52:27 -0500, "Steve Kirsch" <te**@test.co m>
wrote:

I need a simple function that can match the number of beginning and ending
parenthesis in an expression. Here's a sample expression:

( ( "john" ) and ( "jane" ) and ( "joe" ) )

Does .NET have something built-in that can accomplish this, or do I have to
write my own parser? I don't want to reinvent the wheel if possible.

private bool IsValidString(s tring expression)
{
int balance = 0;
foreach(char c in expression)
switch(c)
{
case '(':
balance++;
break;
case ')':
if(--balance < 0)
return false;
break;
}
return balance == 0;
}

--
Marcus Andrén

[Kevin Spencer]

How about a Regular Expression?

The following Regular Expression will capture all opening and closing
parentheses. It puts opening parentheses into Group 1 ("opening"), and
closing parenthese into Group 2 ("closing"):

(?<opening>[\(])|(?<closing>[\)])

Using the Regex Class, you can count the number of each group separately.

--
HTH,

Kevin Spencer
Microsoft MVP
..Net Developer
Ambiguity has a certain quality to it.
..
"Steve Kirsch" <te**@test.co m> wrote in message
news:%2******** ********@TK2MSF TNGP15.phx.gbl. ..

I need a simple function that can match the number of beginning and ending
parenthesis in an expression. Here's a sample expression:

( ( "john" ) and ( "jane" ) and ( "joe" ) )

Does .NET have something built-in that can accomplish this, or do I have
to write my own parser? I don't want to reinvent the wheel if possible.

[Bill Butler]

"ALI RAZA" <al************ *@yahoo.com> wrote in message
news:%2******** ********@TK2MSF TNGP15.phx.gbl. ..

Salam

The simple solution to this problem is to implement a stack, when u encounter '(' push it on the
stack, and when u encounter ')', pop it from the stack.

In the End, check if the stach is empty, if it is empty then the parenthesis are match else they
are not.

--

All of this assumes that ALL parens should be pushed on the stack.
For instance:
Console.WriteLi ne("(");
would not work.

In a situation like this you might need to make sure the paren is not part of a string.

All of this depends on the use to which the function is being applied.

Bill

[Jon Skeet [C# MVP]]

Kevin Spencer <ke***@DIESPAMM ERSDIEtakempis. com> wrote:

How about a Regular Expression?

The following Regular Expression will capture all opening and closing
parentheses. It puts opening parentheses into Group 1 ("opening"), and
closing parenthese into Group 2 ("closing"):

(?<opening>[\(])|(?<closing>[\)])

Using the Regex Class, you can count the number of each group separately.

That will count them, but not make sure that they match - it would say
that:

)(

is valid, for instance.

--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet
If replying to the group, please do not mail me too

[Kevin Spencer]

True, Jon, but that was not the question asked. A regular expression could
also be developed that would ensure they match. If it were requested, I
would be glad to take the time to do so.

--
HTH,

Kevin Spencer
Microsoft MVP
..Net Developer
Ambiguity has a certain quality to it.

"Jon Skeet [C# MVP]" <sk***@pobox.co m> wrote in message
news:MP******** *************** *@msnews.micros oft.com...

Kevin Spencer <ke***@DIESPAMM ERSDIEtakempis. com> wrote:

How about a Regular Expression?

The following Regular Expression will capture all opening and closing
parentheses. It puts opening parentheses into Group 1 ("opening"), and
closing parenthese into Group 2 ("closing"):

(?<opening>[\(])|(?<closing>[\)])

Using the Regex Class, you can count the number of each group separately.

That will count them, but not make sure that they match - it would say
that:

)(

is valid, for instance.

--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet
If replying to the group, please do not mail me too

[Jon Skeet [C# MVP]]

Kevin Spencer <ke***@DIESPAMM ERSDIEtakempis. com> wrote:

True, Jon, but that was not the question asked.
Well, it asked about "matching" parentheses. I think it's reasonable to
assume that the OP doesn't actually want ")(" to match - especially
given the sample.
A regular expression could
also be developed that would ensure they match. If it were requested, I
would be glad to take the time to do so.

Hmm... I seem to remember something in CS classes saying that this is
something that regular expressions actually can't do. You can develop
them that will match down to a certain level of nesting (i.e. for any
given number of levels of nesting, you can build a regular expression
which will match it), but nothing to match *any* level of nesting. I
could easily be wrong though...

--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet
If replying to the group, please do not mail me too